The present invention relates in an aspect to a laser arrangement for generating a twice frequency-converted laser radiation.
Such a laser arrangement is particularly suitable for generating a single-frequency, low-noise laser light with a wavelength in the UV range.
Numerous lasers with a frequency conversion inside of a resonator are known from prior art, which are employed to generate laser light with a wavelength in the UV range. The frequency conversion inside of a resonator here serves to increase the frequency of the initially generated laser light in order to generate, proceeding from longer-wave laser light, short-wave laser light with a wavelength in the UV range.
From DE 103 39 210 A1 a laser arrangement is known, in which altogether three laser resonators, arranged one after the other, are provided in order to obtain twice frequency-converted laser light. The first laser resonator serves for generating a fundamental wave, the second laser resonator for generating the second harmonic (first overtone) and the third laser resonator for generating the fourth harmonic (third overtone). The individual resonators must be coupled with a complex optics in order to enable an efficient transition of the laser light to be converted from one resonator to the next resonator.
From U.S. Pat. No. 5,621,744 A a laser arrangement is known, having a first frequency conversion stage inside of a resonator and an external second frequency conversion stage. The external second frequency conversion stage is here designed as a circular laser resonator. In such an arrangement, also, a comparatively complex optics is necessary in order to ensure a correct coupling of the laser radiation into the second frequency conversion stage.
From DE 42 28 862 A1 a laser arrangement is known, in which two laser resonators are coupled with each other and in which the laser light circulating in the two resonators partially radiates through a joint section of both resonators. The drawback of this arrangement is the use of a so-called multimode laser, which emits multi-frequency laser light, has a small coherence length and, moreover, has undesirable amplitude noise in the generated laser light.
From DE 101 18 793 A1 a laser arrangement is known, in which two non-linear crystals are arranged in a joint resonator in order to in this manner attain a two-fold frequency conversion of the laser light radiated into it. By refraining from the use of a further laser resonator, this arrangement can be designed in an optically less complex manner. However, the drawback is that the efficiency of the arrangement is low if only one frequency circulates in the laser resonator while resonating. If in the arrangement all the generated frequencies are made resonant, then undesirable amplitude noise can likewise occur in the emitted laser radiation.